The present invention relates to the discovery that a group of 3,4-(diphenyl)chromans are useful for lowering serum cholesterol and inhibiting smooth muscle cell proliferation, particularly, restenosis, in humans, and inhibiting endometriosis and uterine fibroid disease in women.
All mammalian cells require cholesterol as a structural component of their cell membranes and for non-sterol end products. The very property, however, that makes cholesterol useful in the cell membranes, its insolubility in water, also makes it potentially lethal. When cholesterol accumulates in the wrong place, for example within the wall of an artery, it cannot be readily mobilized and its presence leads to the development of an atherosclerotic plaque. Elevated concentrations of serum cholesterol associated with low density lipoproteins (LDL'S) have been demonstrated to be a major contributing factor in the development and progression of atherosclerosis.
Estrogen, particularly when taken orally, lowers plasma levels of LDL and raises those of the beneficial high density lipoproteins (HDL's). Long-term estrogen therapy, however, has been implicated in a variety of disorders, including an increase in the risk of uterine cancer and possibly breast cancer, causing many women to avoid this treatment. Recently suggested therapeutic regimens which seek to lessen the cancer risk, such as administering combinations of progestin and estrogen, cause the patient to experience unacceptable bleeding. Furthermore, combining progestin with estrogen seems to blunt the serum cholesterol lowering effects of estrogen. The significant undesirable effects associated with estrogen therapy support the need no develop alternative therapies for hyperlipidemia/hypercholesterolemia that have the desirable effect on serum LDL but do not cause undesirable effects.
Attempts to fill this need by the use of compounds commonly known as antiestrogens which interact with an estrogen receptor and/or bind with what has been termed the antiestrogen binding site (AEBS) have had limited success, perhaps due to the fact that these compounds generally display a mixed agonist/antagonist effect and are subject to the same adverse effects associated with estrogen therapy.
The present invention provides methods for lowering serum cholesterol levels without the associated adverse effects of estrogen therapy, and thus, provides an effective and acceptable treatment for hyperlipidemia/hypercholesterolemia.
Smooth muscle cell proliferation plays an important role in diseases such as atherosclerosis and restenosis. Vascular restenosis after percutaneous transluminal coronary angioplasty (PTCA) has been shown to be a tissue response characterized by an early and late phase. The early phase, occurring hours to days after PTCA, is due to thrombosis with some vasospasms while the late phase appears to be dominated by excessive proliferation and migration of smooth muscle cells. In this disease, the increased cell motility and colonization by smooth muscle cells and macrophages contribute significantly to the pathogenesis of the disease. The excessive proliferation and migration of vascular smooth muscle cells may be the primary mechanism to the reocclusion of coronary arteries following PTCA, atherectomy, laser angioplasty, and arterial bypass graft surgery. See "Intimal Proliferation of Smooth Muscle Cells as an Explanation for Recurrent Coronary Artery Stenosis after Percutaneous Transluminal Coronary Angioplasty," Austin et al., Journal of the American College of Cardiology 8:369-375 (August 1985).
Vascular restenosis remains a major long term complication following surgical intervention of blocked arteries by percutaneous transluminal coronary angioplasty (PTCA), atherectomy, laser angioplasty, and arterial bypass graft surgery. In about 35% of the patients who undergo PTCA, reocclusion occurs within three to six months after the procedure. The current strategies for treating vascular restenosis include mechanical intervention by devices such as stents or pharmacologic therapies including heparin, low molecular weight heparin, coumarin, aspirin, fish oil, calcium antagonist, steroids, and prostacyclin. These strategies have failed to curb the reocclusion rate and have been ineffective for the treatment and prevention of vascular restenosis. See "Prevention of Restenosis after Percutaneous Transluminal Coronary Angioplasty: The Search for a `Magic Bullet`," Hermans et al., American Heart Journal 122:171-187 (July 1991).
In the pathogenesis of restenosis, excessive cell proliferation and migration occurs as a result of growth factors produced by cellular constituents in the blood and the damaged arterial vessel wall which mediate the proliferation of smooth muscle cells in vascular restenosis.
Agents that inhibit the proliferation and/or migration of smooth muscle cells are useful in the treatment and prevention of restenosis. The present invention provides for the use of compounds as smooth muscle cell proliferation inhibitors.
Unterine fibroid disease (uterine fibrosis) is an old and ever present clinical problem which goes under a variety of names, including uterine hypertrophy, uterine lieomyomata, myometrial hypertrophy, fibrosis uteri, and fibrotic metritis. Essentially, uterine fibroid disease is a condition where there is an inappropriate deposition of fibroid tissue on the wall of the uterus.
This condition is a cause of dysmenorrhea and infertility in women. The exact cause of this condition is poorly understood but evidence suggests that it is an inappropriate response of fibroid tissue to estrogen. Such a condition has been produced in rabbits by daily administrations of estrogen for 3 months. In guinea pigs, the condition has been produced by daily administration of estrogen for four months. Further, in rats, estrogen causes similar hypertrophy.
The most common treatment of uterine fibroid disease involves surgical procedures which are both costly and sometimes a source of complications such as the formation of abdominal adhesions and infections. In some patients, initial surgery is only a temporary treatment and the fibroids regrow. In those cases, a hysterectomy is performed which effectively ends the fibroids, but also the reproductive life of the patient. Also, gonadotropin releasing hormone antagonists may be administered, but their use is tempered by the fact they can lead to osteoporosis.
Endometriosis is a condition of severe dysmenorrhea, which is accompanied by severe pain, bleeding into the endometrial masses or peritoneal cavity, and often leads to infertility. The cause of the symptoms of this condition appear to be ectopic endometrial growths which respond inappropriately to normal hormonal control and are located in inappropriate tissues. Because of the inappropriate locations for endometrial growth, the tissue seems to initiate local inflammatory-like responses causing macrophage infiltration and a cascade of events leading to initiation of the painful response. The exact etiology of this disease is not well understood and its treatment by hormonal therapy is diverse, poorly defined, and marked by numerous unwanted and perhaps dangerous side effects.
One of the treatments for this disease is the use of low dose estrogen to suppress endometrial growth through a negative feedback effect on central gonadotropin release, and subsequent ovarian production of estrogen. However, it is sometimes necessary to use continuous estrogen to control the symptoms. This use of estrogen can often lead to undesirable side effects and even the risk of endometrial cancer.
Another treatment consists of continuous administration of progestin which induces amenorrhea and, by suppressing ovarian estrogen production, can cause regressions of the endometrial growths. The use of chronic progestin therapy is often accompanied by the unpleasant central nervous system side effects of progestin, and often leads to infertility due to suppression of ovarian function.
A third treatment consists of the administration of weak androgens, which are effective in controlling the endometriosis. However, they induce severe masculinizing effects. Several of these treatments have also been implicated in causing a mild degree of bone loss with continued therapy.
Therefore, new methods of treating endometriosis are desirable.